HA architecture Flashcards
name the 3 types of load balancers
network, app, classic
_____ load balancers are best suited for load balancing of HTTP adn HTTPS traggic. they operate at layer 7 and are app aware. they are intelligent, and you cna create advanced request routing, sending specified requests to specific web servers.
application
____ are best suited
for the load balancing of TCP traffic
where extreme performance is required.
Network
Network load balancers operate at layer ___4
4
these load balancers are capable of handling millions of requests per second, while maintaining ultra-low latencies.
used for extreme performance
network
____ load balancers are the legacy elastic balanders. you can load balance http/https apps and use layer 7 specific features, such as x-forwarded and sticky sessions. you can also use strict layer 4 load balancing for apps that rely purely on the TCP protocol.
classic
with classic load balancers, If your application stops responding,
the ELB is going to respond with a ___ error.
This means that the app is having issues. this could be either at the web server layer or the db layer. identify where the app is failing, and scale it upor out where possible.
504
what does x-forwarded for header do?
shows the user’s public IP address
instances monitored by ELB are reported as :
what 2 things?
inservice or outofservice
t or false
you get an ip and a dns name for your LB
false, you only get dns name. no IP
Classic Load Balancer’s routes each request
independently to the registered EC2 instance
with the smallest load
and what ___ ____ allows you to do
is to bind a user’s session to a specific EC2 instance.
So, you’re gonna stick a user session
to a particular EC2 instance and this ensures
that all requests from the user during the session
are sent to the same instance.
sticky sessions
you can also enable sticky sessions
for Application Load Balancers as well,
but this time, the traffic will be sent
at the___ ____ level rather than
at the individual EC2 instance.
target group
So, a common exam scenario will be
you’ve got a user, they’re using Route 53,
100% of the traffic’s being sent to a load balancer
in us-east-1a and that load balancer is sending that traffic
on to its four instances which are
in the same Availability Zone as it,
and then you log in to us-east-1b
and you notice that this EC2 instance
is not getting any traffic at all.
What should you do?
Well, you should enable _____ load balancing
and that way, it will get traffic
because it’s in another Availability Zone
and you haven’t enabled ____ load balancing.
cross-zone
you can create a listener with rules
to forward requests based on the URL path
and this is known as _____ routing.
So, if you are running microservices,
you can route traffic to multiple back-end services
using ____ routing.
For example, you can route general requests
to one target group and requests to render images
to another target group.
path-based
what are the three components of auto scaling?
groups, configuration templates, and different scaling options
what is an AUto scaling group
a logical component. ie: web server group, app group, db group, etc.
what are config templates concerning auto scaling?
groups uses a lunch template of launch config as a config template for its ec2 instances. you can specify info such as the AMI id, instance type, key pair, SG, and block device mapping for you instances
what are scaling options in regards to auto scaling?
scaling optioned provides several ways for you to scale your auto scaling groups. for example, you can configure a group to scale based on teh occurance of specified conditions(dynamic scaling) or on a schedule
what are the 5 different scaling options?
There’s maintain the current instance levels at all times.
There’s scale manually.
There’s scale based on a schedule.
There’s scale based on demand.
And then there’s using predictive scaling
what is predictive scaling?
scales based on previous performance
So you might get some exam questions talking about
highly available architecture, so you might have a website
that requires a minimum of six instances
and it must be highly available.
And you must also be able to tolerate the failure
of one availability zone.
So you are always gonna need six instances
and you can tolerate one availability zone.
So what is the ideal architecture for this environment
while being the most cost effective?
we’re always going to need
three availability zones with three instances
to meet this requirement.
We’re gonna need nine instances total.
That way if we lose one AZ we still got six instances
that will be able to look after our environment.
Read Replicas is for disaster recovery
t or f
f
Read Replicas is for performance.
what is the difference between scaling up and scaling out?
So scaling out is where we use Auto Scaling group
and we add additional EC2 instances.
Scaling up is where we increase the resources
inside our EC2 instances,
so we might go from a T2 micro to a 6X extra large
or something like that.
which s3 buckets are not HA?
1 zone IA
and reduced redundancy
what is quick start?
a bunch of cloudformation templates already built by SAs allowing you to create complex environments very quickly.
In discussions about Cloud services the words ‘Availability’, ‘Durability’, ‘Reliability’ and ‘Resiliency’ are often used. Which term is used to refer to the likelihood that a resource ability to recover from damage or disruption?
resiliancy
In discussions about Cloud services the words ‘Availability’, ‘Durability’, ‘Reliability’ and ‘Resiliency’ are often used. Which term is used to refer to the likelihood that a resource will continue to exist until you decide to remove it?
durability
In discussions about Cloud services the words ‘Availability’, ‘Durability’, ‘Reliability’ and ‘Resiliency’ are often used. Which term is used to refer to the likelihood that a resource will work as designed?
reliability
